Some compounds such as Diprotin A and B (J. of Antibiotics, 37, 422-425 (1984)) have been known as physiologically active substances having the dipeptidylpeptidase IV inhibitory activity.
These compounds, however, are weak in their inhibitory activity against the above enzyme and are unsatisfactory for use as a physiologically active substance in the above medicinal and pharmaceutical preparations. Therefore, the advent of a novel compound which is suited for such uses has been waited.